"water test" for residential heat exchangers - thoughts?

>I'm curious on opinions from pro's of the water test for residential
>heat exchangers advocated by Ellis Prach of
>http://www.heatexchangerexperts.com/ In this test, the tech pulls the
>blower, douses the exchanger with a water solution from a large
>sprayer, and then looks inside the combustion area for water
>penetration. If there's water getting in, they reason, you have a
>breached heat exchanger that they recommend replacing it.
>I'm suspicious of this Prach guy though... a self-proclaimed heat
>exchanger expert, and evidently pontificates--in his seminars he holds
>all over the country training HVAC techs--that he can even find leaks
>in a heat exchanger that's 3 years old. His seminars are apparently
>quite hands-on and he travels with several actual heat exchangers and
>demonstrates trouble spots on each. I've talked to two attendees and
>they concur on these points.
>So, do y'all think this is a worthwhile diagnostic test that
>correlates with real safety issues, or just a great way to sell new
>furnaces and make this Prach guy rich giving seminars from companies
>so willing to have him teach techs to find leaks in 3 year old heat
>exchangers?
>The whole thing seems to hinge on the assumption that if the heat
>exchanger isn't water tight, then it isn't air tight, and the further
>assumption that pressures inside the furnace are such that combusion
>byproducts might actually make it into the airflow of such leakage
>areas.
>My own situation that motivates the question: a tech (from a
>significant, well-respected company in Chicagoland that I've used for
>years because they invest in training their techs rather well) had
>attended a seminar by this man recently, and had come to give my 15
>year old Carrier furnace the annual cleaning and once over. Perhaps
>it was the age of the furnace, or the rust on it from the prior owner
>not occupying hte house for the prior two years, but soething
>compelled him to drop the blower and perform this new test he'd
>learned recently. Now, this is a furnace that had a visual inspection
>and tested CO free on all chambers last November for whatever that's
>worth. I understand that for CO to form and get into ducts you need a
>lot more than an HX breach.
>Personally, I may go ahead and replace the furnace based on age and
>the suspicion alone, and enjoy the comfort and efficiency afforded by
>a newer 2-stage and/or variable speed furnace since my time horizons
>in this home are long enough to get the payback.
>But I remain curious what folks think about this test all the same,
>and the likelihood that my current furnace _really_ has a safety
>concern.
>Thanks in advance for any constructive thoughts or discussion.
>Best Regards,

> Seems you've already made up your mind but I'll give you my .03
> worth. I previously worked for a national hvac company that adopted
> this practice like it came from the bible. This company was also into
> high pressure sales practices and tactics. One little twist they added
> to the test was to make sure the heat exchanger was nice and hot right
> before they started spraying water on the heat exchanger. Common sense
> tells you that hot thin metal and cold water are not a good
> combination for a homeowners heat exchanger. CO tests, detectors and
> visual inspections and cameras are a more advanced way of checking
> heat exchangers.
> Bubba

>I'm not going to waste a lot of time on this "new" technique.